Animating the process of creating a 3d scene
After setting up the animation in blender, render out the final video. Then do an opengl render of the 3d scene, this will render the 3d viewport version of the animation. You can adjust the display and object properties to adjust how the scene looks.

Once you have the two videos, add them to the Video Sequence Editor, then you can cut the strips so that each is visible at different times. You can add a wipe effect to switch between each video or you can use animated masks for more elaborate transitions.